This would be the 'Caddy' I would use to replace the optical drive, but I was thinking to put the current HDD into the caddy instead of the SSD and put the SSD in the main place where the current HDD is. Any issues with this?

I plan to buy a 128GB Crucial M4 SSD for my Apps/Music/Lightroom Library ect. However, i was also thinking whether i should just replace the current HDD with the SSD and use the current HDD as an External Hard Drive instead; but I don't particularly want to bring that with me everywhere I go thats why I would like to have that in my Mac rather than out.

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